Process for manufacture of high sheen bifilament yarn and elastic textile article

ABSTRACT

A BIFILAMENT YARN COMPRISING TWO SYMMETRICAL LOBES FUSED SO THAT THE CONCAVE SIDES INTERCEPT AT ANGLE 0 RANGING FROM 10 TO 54*. THE YARN HAS A BROAD CONCAVE AREA AND A NARROW EDGE AREA OF CONVEX SHAPE AND PREEFRABLY A MODIFICATION RATIO OF BETWEEN 1.65 AND 3.0. THIS BIFILAMENT YARN, TEXTURED AND NON-TEXTURED, SEMIDULL AND BRIGHT, WHEN CONVERTED TO PLAIN KNIT HOISERY HAS A LUSTER IN THE RANGE OF 6.6 TO 21 (K/SX100) UNITS. THE TEXTURED AND NON-TEXTURED PLAIN KNIT TEXTILE ARTICLES CONSISTING OF THE BIFILAMENT YARNS OF THIS INVENTION AFTER REPETITIVE ELONGATIONS OF 25 PERCENT HAVE 150-300 PERCENT GREATER WORK OF RECOVERY AND EQUAL IMPROVEMENT IN RESISTANCE TO SAGGING AND WRINKLING THAN OTHER CROSS-SECTIONAL CONFIGURATIONS. THE BIFILAMENT YARNS ARE PREPARED BY MELT SPINNING THERMOPLASTIC HOMOPOLYMERS HAVING A RELATIVE FORMIC ACID VISCOSITY OF 25 TO 90 AT A TEMPERATURE OF 250-280*C. THROUGH TWIN ORIFICES SEPARATED FROM EACH OTHER FOR A DISTANCE OF 0.05 TO 4.0 MILS.

June 5, 1973 G TUR ET 3,737,505

PROCESS FOR MANUFACTURE OF HIGH SHEEN BIFILAMEN'I YARN AND ELASTICTEXTILE ARTICLE Filed May 28, 1971 4 Sheets-Sheet 1 (0 Lu .J (9 ZSPARKLE EFFECT AT TWIST\: POINT m HOSIERY OR 0 FABR|C. I L V 1.4 1.5 (L6L1 L8 L9 2.0 2.| 2.2 2.3 2.4 2.5 2.6

MODIFICATION RATIO FIG. 2

I 1 -l I 35 1 LOOK P-SPARKLE so I SLICK LOOK .2 I HIGH ,2 SHEEN 8 25 I l2 l v J; 20 I FALSE TWIST l NON-TEXTURED BIFIL YARN\ BIFIL YARN g l5 i-S 1 I -I I0 I I l l 5. I i I I 0 I L0 1.5 2.0 2.5 5.0 MODIFJCATION RATIOFIG. 3 INVENTORS RALPH W. SCHUETTLEF GARLAND L. TURNER GEORGE H.COLLINGWOOI ATTORNEY June 5, 1973 G. TURNER ET AL 3,737,505

H SHEEN BIFILAMENT PROCESS FOR MANUFACTURE OF HIG YARN AND ELASTICTEXTILE ARTICLE 4 Sheets-Sheet 2 Filed May 28, 1971 FIG.5

FIG.7

INVENTOR.

m m o, LRW TEG BM m U U H T HT C A .E M WW E HAG PLR LRO AAE RGG June1973 G L. TURNER ET AL 3,737,505

PROCESS FOR MANUFACTURE OF Hum SHEEN BIFILAMENT YARN AND ELASTIC TEXTILEARTICLE Filed May 28, 1971 4 Sheets-Sheet :5

INVENTORS RALPH W. SCHUETTLER GARLAND L TURNER GEORGE H. COLLINGWOOIGRAMS LOAD GRAMS LOAD June 5, 1973 Filed May 28 1971 I LENGTHWISEBICONPONENT f lst CYCLE IO 20 3O ELONGATION FIG. l4

F.T. FALSE TWIST TRIANSVERISE F.T. BIFIL ELONGATION FIG. I?

F.T. FALSE TWIST GRAMS LOAD GRAMS LOAD G L. TURNER ETAL PROCESS FORMANUFACTURE OF HIGH SHEEN BIFILAMENT YARN AND ELASTIC TEXTILE ARTICLELENGTHWISE (I) 2 2 CZ 9 o lo 20 so ELONGATION FIG. l5

TRANSVERSE g 50 O J ELONGATION FIG. l8

4 Sheets-3heet 4 LENGTHWISE ET. ROUND 2o ELONGATION FIG. I6

TF'KANSVER'SE BICOMPONENT 2 0 ELONGATION FIG. l9

INVENTORS PROCESS FOR MANUFACTURE OF HIGH SHEEN BIFILAMENT YARN ANDELASTIC TEXTILE ARTICLE Garland Linwood Turner, Chesterfield, Va., RalphWilliam Schuettler, Fuguay Varina, N.C., and George Howard Collingwood,West Warwick, R.I., assignors to Allied Chemical Corporation, New York,N.Y.

Continuation-impart of applications Ser. No. 733,556

and Ser. No. 733,557, both May 31, 1968. This application May 28, 1971,Ser. No. 148,125

Int. Cl. B28h 21/54 US. Cl. 264-177 F 3 Claims ABSTRACT OF THEDISCLOSURE A bifilament yarn comprising two symmetrical lobes fused sothat the concave sides intercept at angle ranging from to 54. The yarnhas a broad concave area and a narrow edge area of convex shape andpreefrably a modification ratio of between 1.65 and 3.0. This bifilamentyarn, textured and non-textured, semidull and bright, when converted toplain knit hosiery has a luster in the range of 6.6 to 21 (K/SX 100)units. The textured and non-textured plain knit textile articlesconsisting of the bifilament yarns of this invention after repetitiveelongations of 25 percent have 150-300 percent greater work of recoveryand equal improvement in resistance to sagging and wrinkling than othercross-sectional configurations. The bifilament yarns are prepared bymelt spinning thermoplastic homopolymers having a relative formic acidviscosity of 25 to 90 at a temperature of 250-280 C. through twinorifices separated from each other for a distance of 0.05 to 4.0 mils.

BACKGROUND OF THE INVENTION This is a continuation-in-part' applicationof Ser. Nos.

733,556 and 733,557, filed May 31, 1968, now aban-' doned.

Ladies stretch hosiery has usually been made from false-twisted roundcross section yarn or bicomponent yarn where one component is ahomopolymer and the other component is a copolymer arranged either sideby side with the homopolymer or as a core in a sheath and corearrangement. Such yarns, while finding utility in ladies hosiery, have adisadvantage in that three or more sizes are required to cover the rangeof sizes 8 /2 to 11 /2. This range of sizes amounts to about 99 percentof the ladies hosiery consumption in the United States. Additionally,various cross-sectional types such as trifllament, triangular, Y-crosssection, star cross section, polygonal, and the like, have been employedto achieve decorative effects in these hosiery. When these conventionalyarns are employed, three or more sizes are required to cover thepractical range of hosiery sizes, and generally, the modified hosieryhas either too dull an appearance or too much glitter with the latterhaving utility only for its novelty effect.

There has long been a need for a true stretch hosiery where one sizewill fill the majority of end-use requirements and which has sufficientluster and sheen to be desirable for formal wear without being toograish for everyday and business use. It is also highly desirable toproduce a true stretch yarn having adequate power of recovery tomaintain a good fit without wrinkling or becoming permanently deformedunder severe bending action, such as deep-knee bends. Additionally,hosiery yarns made from two components, a homopolymer and a copolymer,are expensive and diflicult to produce. Thus,

United States Patent O there has long been a need to produce a stretchyarn which avoids the described problems, and more particularly, it hasbeen desirable to produce said yarn from a single homopolymer.

In an attempt to simulate some of the geometric forms of natural fibers,various configurations including bifilament yarns were produced almostfour decades ago from man-made cellulosic fibers as disclosed in SwissPat. 145,408 dated Feb. 28, 1931. Since this time, several patents havebeen issued showing various configurations representing a range of fibertypes which have two or more lobes. For example, US. Pats. 3,156,607 and3,131-

427 illustrate yarn configurations which are essentially bilobal. Thus,the prior art is replete with patents showing various types of bilobalyarns yet none of the patentees recognized the critical nature of theangle of intercept between the two lobes which is essential in producinga high sheen hosiery yarn that does not have a garnishness related toexcessive sparkle.

Additionally, when such multilobed forms are used in ladies hosieryirrespective of the texturing method emplyoed, three or more sizes ofstretch hosiery are required to cover the range of consumer sizes.Indeed, to have truly satisfactory fits in stretch hosiery, five sizesare judged by independent laboratories as being necessary to suit mostconsumer'requirements for a comfortable and attractive fit.

There has been still another problem with prior art yarns in that thestretch qualities on repeated stretching of hosiery results in continuedloss of the orignal stressstrain properties and sagging or wrinkling ofthe hosiery may occur, particularly at the ankle section and kneesection. With the foregoing discussion in mind, the provision for ahomopolymer yarn which possesses the de sired appearance factors as wellas the desired stretch properties representsa substantial improvement inthe art.

SUMMARY OF THE INVENTION The product of this invention involves athermoplastic homopolymer fused into an oblong shape having twosy-mmetrical lobes fused so that the concave sides intercept at an angle0 ranging from 10 to 54, and preferably at angle 0 42 to 52, and 16 to38. The bifilament yarn has a broad concave area and a narrow edge(convex) area so that when said yarn is placed in-a knit structure, thebroad concave areas become aligned facing each other at stitch crossingpoints to present a convex or edge area to view and twist 90 or more topresent the, concave or broad areas to view in the loop sections. Lightreflects from each concave area presented to view in the loop areas as aminute point flash and the alignment of these minute point flashesresult in a sheen, opalescence, shimmer or scintillation point sometimescalled scintilla look which is enhanced in bright yarns and reduced if adelusterant 'is present. Because of its geometrical configurationfalse-twist bifilament yarn has twice the number of twists trapped ineach loop and twice the number of point flashes; therefore, an enhancedluster or sheen is obtained in plain-knit hosiery.

Likewise, this twist trapped in each loop of the knitted structure givesgreatly increased multidirectional elastic properties to the gridstructure since each twist in each loop, coarse and wale becomes amultiple of the total number of loops of the grid structure therebygreatly enhancing its elasticity.

The preferred modification ratios are 1.65 to 3.0 and more preferably1.75 to 2.8 and the most preferable 1.75 to 1.95 the tip radius isgenerally 0.9 or greater but less than 1.2. The bifilament yarns,textured and non-textured, sernidull and bright, when converted to plainknit hosiery as an undyed boardered structure have luster values asfollows:

Bright non-textured: 9 to 40 (K/SX 100) units Bright false-twist: 12 to45 (K/Sx 100) units These high luster values are due to alignment ofminute point flashes resulting in a high glossy sheen termed the glaclook or wet look for bright yarns. This high sheen and uniform lusterhas not thus far been obtained in prior art knitted structures.

The preferred process for producing the yarn as above described involvesemploying a polyamide having a relative formic acid viscosity of between25 and 90 which is extruded through a pair of spinnerette orificeshaving a distance between said orifices of 0.5 to 4.0 mils, preferably1.0 to 3.5 mils. Nylon 6 is spun at a temperature of between 250 and 280C., preferably 265 to 275 C., and nylon 6,6 is spun at approximately 10higher temperature. The polyamide relative formic acid and the distancebetween the spinnerette orifices are the two major 'variables asindicated hereinafter in Table 1. With an increase in relative formicacid viscosity, the modification ratio increases and the angle ofintercept decreases and the luster values increase. Thus, a sparkle lookis produced and the desired high sheen glac look is lost. It is noted,also, that the temperature of the polymer melt must be considered. Astemperature increases, the modification ratio decreases. Additionally,at too high a temperature, drips, breaks and warps may appear, which areundesirable in the processing of such fibers.

Thermoplastics in general can be employed for producing bifilamentyarns, but because of their excellent dyeing properties and good opticalproperties, polyamides usually are preferred for the production ofbifilaments in accordance with this invention. Preferred polyamides arepoly-e-caprolactam (nylon 6), polyhexamethylene adipamide (nylon 6,6),and the polyamides made by condensation of p,p'-bis(para-aminocyclohexyl)methane with dodecanedioic acid to produce thepolyamide poly[bis(p aminocyclohexyl)methane dodecamide].

The bifilament yarns disclosed as the invention herein also have utilityin transport upholstery and apparel end uses because of the highelasticity of the knitted structure and the high glossy sheen or glaclook which characterizes knitted textile articles made from brightbifilaments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross section of thespinnerette orifices employed to extrude the bifilament yarns of thepresent invention.

FIG. 1A is a cross-sectional 'view representing the bifilament yarn ofthis invention illustrating how the angle of intercept is measured.

FIG. 2 illustrates graphically the relationship between the opticalproperties of the filaments as a function of the angle of the bifilamentintercept point versus the modification ratio.

FIG. 3 is a graph illustrating the lusture of bifilament yarns of thisinvention plotted against the modification ratio. These data illustratethe change in sheen between false-twist and normal yarn. The dottedlines show the range of modification ratio which produces the preferredhigh sheen yarn. The area to the right of the dotted lines shows therange of modification ratio which produces the "scintilla look.

FIG. 4 is a photograph illustrating, at 320 magnifications,representative cross sections of undrawn bifilament yarns of the instantinvention which have a modification ratio of 1.7.

FIG. 5 is another photograph at 320 magnifications of other bifilamentundrawn cross sections which have a high sheen glac look when the yarnis placed in a sheer fabric. Generally, above this modification ratio of2.0, a transition to the sparkle look occurs.

FIG. 6 is a photograph at 560 magnification of a typical cross sectionof drawn bifilament yarns having a modification ratio of 2.3 to 2.4,which illustrates the bifilaments of this invention.

FIG. 7 is a photograph at 900 magnifications of a drawn bifilament yarnhaving a modification ratio of 2.8 to 2.9, which produces the scintillalook.

The yarns of FIGS. 6 and 7 are outside the critical range required toobtain a glac look.

FIG. 8 is a photograph illustrating the unique property obtained bycombination of bifilament geometry with a false-twist operation. Thisillustrates the alignment of the concave surfaces at stitch cross-overpoints and the twist which in the loop part exposes the broad parts ofthe concave surfaces to view. This additionally illustrates the alignedrows of point light reflections from concave surfaces to give the uniquesheen which can be observed. The magnification of FIGS. 8 through 13 is36X.

FIG. 9 is a bifilament yarn in jersey knit hosiery which was notfalse-twisted. There is similar twist entrapment and alignment of thelight reflective areas as in FIG. 8.

FIG. 10 is a photograph of a round cross-sectional yarn which isfalse-twisted and knit into hosiery. It can be observed that the lightreflective areas are completely random, there is no twist between thestitches, and the yarn tends to curl back on itself rather than betwisted between the stitches.

FIG. 11 is a photograph of round monofilaments of plain knit hosiery. Italso lacks the properties of twist entrapment and luster effectscharacteristic of bifilament yarns as illustrated in FIG. 9.

FIG. 12 is a photograph of stretch hosiery of round cross section,bicomponent filaments. Again, there is no alignment of the light areasin the yarn. Consequently, there is no luster or sheen, or enhancementof the elastically from twist trapped between stitches.

FIG. 13 is a photograph of mesh hosiery tuck stitch made from trilobalor triangular shaped yarns. As can be observed, the light reflectionareas are random and significantly larger than those illustrated inFIGS. 8 and 9. Such yarns while suitable for many novelty end-uses haveutility only as novelty yarns because of the garishness of the luster.

FIG. 14 is a graph illustrating the force required to elongate abicomponent stretch yarn after one cycle of elongation, and, after sixcycles of elongation. The stretch direction was lengthwise and the testsample was ladies hosiery with plain knit construction.

FIGS. 15 and 16 represent the same test parameters as for FIG. 14 exceptthat FIG. 15 represents false-twist bifilament yarns of this inventionwhich have superior elastic properties over that for FIG. 14 and FIG.16. FIG. 16 represents false-twist round cross section nylon 6 yarns.

FIGS. 17, 18 and 19 represent, respectively, leg sections of ladieshosiery made from false-twist bifilament yarn, false-twist roundfilament yarns and round cross section bicomponent sheath and core yarn.The nature of the test data illustrated in these figures is similar tothat described for FIGS. 14, 15 and 16, except the measure ment is inthe transverse direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The bifilament yarns of thepresent invention preferably are spun from a polyamide such as nylon 6or nylon 6,6 directly from a continuous polymerization system whereinthe polymers are melted prior to extrusion using an extruder or amelter. The molten polymer is then extruded through a pair of orificesin close proximity to each other as depicted in FIG. 1 by capillaries 1and 3. These capillaries are separated by the portion 2 which ispreferably an integral portion of the spinnerette plate 6. The moltenpolyamide polymer enters through an entry orifice denoted at 5 and isdivided into separate streams on contacting metallic portion 2. Thedistance between orifices 1 and 3 should be between 0.5 and 3.0 mils-Thedistance when less than 0.5 mil results in the separator portion or web2, too weak to withstand the extrusion pressure. Should the distancebetween orifices 1 and 3 exceed 3.0 mils, one then enters the region ofa sparkle effect and the preferred glac look is not obtained. The lengthof spinnerette orifice 4 should generally be in the region of 0.8 to 4times the diameter of the spinnerette orifices 1 to 3, preferably alength to diameter ratio of about 1.2 should be employed.

The yarn product of one part of the present invention has a glac lookwhich has been described as a wet look when fashioned into articles suchas ladies hosiery and other sheer garments. This appearance is achievedonly when specific critical parameters are observed during theproduction of the bifilament yarns of this invention. It is essentialthat the yarns intercept at an angle of between 41 and 54 of the joinedfilaments. It is also preferred that the yarns have a modification ratiorang ing from 1.65 to 2.05. At an intercept angle of greater than 54,too low a luster is obtained and twist is not trapped between thefilament loops to achieve the desirable elasticity properties in knitstructures. At an angle of intercept below 41, the yarn exhibits asparkle effect and does not have the glac look and desirable opalescentsheen of the product made in accordance with this invention.

The angle of intercept is determined by completing the two circlesoutlined by the filament lobes 12 and 14, then completing a linebisecting the center of the circles and the point where the circlesintercept as shown in FIG. 1A. The angle of intercept is the angle 0between the horizontal line passing through the center and the linedrawn to the intercept point.

The modification ratio is determined by dividing the minimum width atthe point of upper and lower intercept points of the two circles intothe length or the distance to the outer perimeter of the two circles.The relationship between the angle and the modification ratio is givenin FIG. 2 wherein it is illustrated that as the modification ratiodecreases, the higher the angle of intercept.

As can be observed in FIG. 2, the glac appearance coincides at an angleof intercept between approximately 38 and 56, the area represented byABCD. At a lower angle of intercept, the glac look is lost and a sparkleeffect occurs. At a broader angle of intercept than 54, there isinsufiicient luster and the bifilaments lost most of their ability toalign face to face at stitch cross-over points, the condition whichimparts twist to said bifilaments in the loops between stitches.Therefore, they lose their luster, but most important, they lose theirelasticity because of inability to trap twist between each stitch in theknitted structure. It is especially desirable that an angle of interceptbe present on both sides of the bifilament yarns so that the twist isalways trapped between stitches regardless of which side of the concavesurfaces align at the stitch crossing points.

In FIG. 3 is shown a plot of the modification ratio versus luster.Luster is ascertained by measuring light reflectivity with a Color Eyemanufactured by the Instrument Development Laboratories, Attleboro,Mass. The reflectivity is expressed by the Kubelka Munk equation where:

where R=reflectivity ascertained with the Color Eye at 557 millimicrons.The method for ascertaining the reflectance has been described in Colorand Business, Science and Industry by D. B. Judd; John Wiley and Sons,New York, New York, 3rd printing, February 1967, pp. 434-438. As can beobserved in FIG. 3, the luster values 6 erably 10 to 18 (K/SX 1 00)units. For false-twist filament yarns, the luster values are quitesignificant higher than non-textured bifilament yarn made into hosiery.This is due to the presence of approximately twice as many concavereflection points in each stitch loop of textured over the non-texturedbifilament yarn. Hosiery fashioned from the textured bifilament yarnhave luster values of 14 to 21 (K/SX 100) units. The presence of thisadditional reflective surface or additional number of reflection pointsresults in a considerable enhancement of the desirable glac look overthat obtained from the same hosiery made from non-textured bifilamentyarns. This enhancement of the glac look by a panel jury evaluation ofskilled colourists amounts to 200 to 300 percent increase in theapparent sheen or luster values observed. Non-textured bifilament yarnhas a luster value of 8 to 16 (K/S X100) units. At lower values than theindicated range of bright luster, insuflicient luster is present toproduce a sheen effect at higher luster values, as, for example, greaterthan 16 for the non-textured and greater than 21 for the false-twisthosiery, there is excessive sparkle in the hosiery which tends to limittheir utility to novelty end uses. Generally, within the scope of theluster values indicated, and as shown in FIG. 3, this hosiery is quiteacceptable to be worn in everyday ofiice use and still quite attractiveand desirable for formal wear. The luster values for semidull yarns havethe same modification ratio as brightv yarns are quite different andonly a low level of surface reflectivity is obtained. The major effectis a significant increase in cover due to the visual appearance of thebroad concave surface in the loop section of the knitted structure. Theincrease in cover is 10-20 percent greater than round cross section yarnof the same denier.

A better appreciation for the critical influence that the angle ofintercept and modification ratio of the yarn has upon appearance and theperformance of the yarn of this product of this invention can berecognized from an investigation of FIG. 4 through FIG. 19. FIGS. 4 to 7are photomicrographs of cross sections of bifilaments illustratingproducts of the invention compared with bifilament cross sections thatare outside of the invention. The modof significance are from 9 to 21(K/S 100) units, prefification ratio of the cross sections shown in FIG.4 is 1.7 and as can be observed there is only a slight distinct concavesurface. Thus, the bifilaments having values below 1.5 and are notconcave and generally have neither luster nor the elasticity desired.FIG. 5 is a cross section having a modification ratio of 2.0 whichrepresents the upper limit beyond which excessive sparkle occurs. FIGS.6 and 7 have modification ratios substantially greater than 2.0 andthereby representing yarns outside the scope of this invention.

FIGS. 4 and 5 illustrate the cross section of undrawn yarns and FIGS. 6and 7 illustrate a cross section of drawn yarn. As can be observed,undrawn and drawn cross sections at equivalent magnification haveidentical geometric cross sections.

FIG. 6 is a photograph at 560 magnifications of a typical cross sectionof drawn bifilament yarn with a modification ratio of 2.3 to 2.4. Notethat even though this is a view of random cross sections, there is atendency for the bifilaments to align with the concave surfaces joiningconvex surfaces at maximum frictional contact.

FIG. 7 is a photograph at 900 magnifications of a drawn bifilament yarnhaving a modification ratio of 2.8 to 2.9. In the upper right handcorner can be observed alignment of the concave surface with the convexsurface of essentially equal symmetry. This alignment provides forfrictional resistance which entraps the twist in the loops and presentsthe narrow edge surface to view at stitch crossing points and therebyincrease the sheerness of the hosiery or textile articles beingemployed. However, when the bifilament is in the loop section then thebroad concave surface of the bifilament is in view and it is this broadsurface that provides for additional cover in the delustered yarns.

Again, when referring to FIG. 1A and FIGS. 4 through 7, it can be notedthat when the circle are completed, as indicated in FIG. 1A for circles12 and 14, the total area of this circle is determined and theirmeasured perimeter is divided into the perfect circle enclosing themeasured area. From this arrangement their degree of circularity can beascertained. Preferably the yarns of this invention have a degree ofcircularity of greater than 0.9. Bifilaments having a substantiallylarger deviation from circularity do not have the same sheen andknitting is difficult because of the tendency of such yarns to break outfrom back-up of twist at the needles.

The performance of hosiery fashioned from bifilament yarns made inaccordance with this invention is com pared with hosiery made from otheryarns in FIGS. 8 through 19. These comparisons are made on the knittedstructures since the unusual properties of light reflectivity andelasticity can be observed, and measured only after the yarn is placedin a fabric construction. It should be emphasized that hosiery is usedas a common example; however, bifilament yarns react in a similar mannerin other jersey knit structures, as well as, tricot knit structures,mesh or tuck stitch structures, and rib stitch structures.

FIG. 8 illustrates a section of hosiery fashioned from bifilament yarnshaving a modification ratio of 1.8. The yarn has 31 turns per inch oftwist imparted thereto, utilizing a Leesona 553 Superloft machine. It isknitted into the hosiery using S and Z twist in alternate courses. Itcan be observed from FIG. 8, the light areas are short in length due tothe twist of bifilament yarns between stitches; however, as can benoted, the light areas are all on an approximate similar plane. Thisresults in a diaphanous, luminous sheen, which has been characterized asthe glac look. As the modification ratio of bifilament yarns isincreased, the length of the light flashes increases. As the intensityof the light at these points increases, each individual light-coloredpoint results in a scintillation point, and the luminous sheen effect isreplaced by a sparkle effect. Between each stitch it can be noted thatthe bifilament yarns twist 90 degrees first to present a flat plane toview and over the course of the twist, at least another 90 degrees for atotal of at least 1 80 degrees to present two concave planes to view. Itis this twist superimposed upon the false-twist stretch that lendssufficient elasticity to the hosiery so one size will span the range ofsizes for most consumer end uses.

.Additionally, as the stitches in FIG. 8 are stretched, the twist thatis trapped between the stitches in the manner stated above graduallyuntwist and when tension is released, these twists rewind. Afterstretching, particularly in areas of hosiery where elongations ensue,that is, the areas which have greater propensity to sag or wrinkle, thetwist which has been unwound as the individual stitches are stretchedout, rewind into a normal configuration and provides additional forcesuperimposed on that from the false-twist crimp. Thus, the combinedforces, at low elongation, are adequate to hold the hosiery firm to theankle or firm to the knee without any evidence of sagging or wrinkling.Moreover, such hosiery resists elongation on repetitive cycling.

In FIG. 9, a bifilament yarn the same as in 'FIG. 8, except withoutfalse-twist, illustrates that all light reflection areas are located atrelatively precise points in the center of the plain-knit stitch andalong the sides of the stitch. Thus, the bifils present the interceptpoint on a flat plane in the direction of the light and in the directionof the observers view. In a comparison between the false-twisted andnon-false-twisted yarns, it can be observed that the light areas andstitches are more uniform for the non-twisted yarn, and that the lightareas are in a precisely aligned plane. It is this alignment of thereflection areas, which results in the smooth luminous sheen. This maybe compared with round cross section yarn in FIG. 11 which exerts notwist entrapment and has essentially no light reflective areas.Additionally, it may be compared with a trifiament yarn cross section ina mesh knit as illustrated in FIG. 13, where the point flashes extendover the long length of the tuck stitches and over broad areas of thestandard jersey knit stitches. These broad areas of light reflectionpromote too much sparkle for most end uses, particularly for ofiice wearand additionally as can be noted, there is less or no twist entrapmentbetween stitches in FIG. 13.

FIG. 12 illustrates a time exposure for round cross section bicomponentelastic yarns. As can be observed, only small sparkle areas areobtained, and if it were not for the lengthy time of exposure, thissparkle could not 7 be observed. Additionally, as can be observed, thereis no twist entrapment between the stitches.

In FIG. 13 it can be observed that there is a bright sparkle in thecenter stitch. It is these large point sparkles that follow the entirelength of the stitch which would seem to indicate there is relativelylow level of change in planes of the reflecting surface. Therefore, nosignificant improvement in elastic properties or sheen could be expectedfrom the yarn as illustrated in FIG. 13. Additionally, the sparkle istoo bright except for formal occasions.

FIG. 14 illustrates the stress-strain characteristics of a plain knithose manufactured from a commercial bicomponent round fiber after onecycle and after six cycles. As can be observed, there is almost completeloss of a stretch power after six cycles, particularly at 3 percentelongation. Moreover, the values at 5 percent elongation are quite low.However, after these initial elongations there is a rapid increase inthe gram loading for small increases in the elongation. It is this rapidincrease which is undesirable because there is too much of a load for agiven degree of stretch. This type of loading causes an uncomfortableeffect on the part of the wearer as well as impart stresses to theindividual filaments so that a sudden pick on impact will probablyresult in a run in the hosiery or garment.

FIG. 15 illustrates the lengthwise extension versus stress-strain loadfor a hose constructed the same as in FIG. 14 except the bifilament yarnof this invention which has been false-twisted was employed. As can benoted, the hose has a definite initial loading that is still high aftersix cycles of extension which slopes upward at a substantially lowerrate than that described in FIG. 14. Thus, it has a relatively uniformstretch characteristic maintaining a definite power after repetitivestretching sufiicient to avoid wrinkling or sagging of the hosiery.

FIG. 16 represents hosiery processes in identical manner to thatillustrated in FIG. 15 with the only difference being round crosssection versus bifilament yarns. Again at 3 percent elongation, aftersix cycles, there is no power left in the yarn and sagging or wrinklingcan occur. Additionally, there is considerable greater drop in the loadat 5 percent elongation from the first to the sixth cycle. Generallythere is a slower increase in loading with a substantial increase inelongation for the round false-twist yarn than that for the bifilamentyarn, as illustrated in FIG. 15, when tested in a lengthwise direction.

False-twist triangular or trilobal cross section yarn is converted intohosiery and processed in identical manner to that as illustrated in FIG.15 with the only difference being round cross section bifilament yarnversus the round cross section of FIG. 16. Again this cross sectionexhibits very low load capacities after six cycles which is similar tothat for round cross section false-twist yarn, except that at .10percent elongation and above, loading is very rapid,

even more rapid than that illustrated in FIG. 15. This would cause anuncomfortable effect on the part of the wearer as well as stressindividual filaments to increase the potential of runs or breakage ofthe filament from sudden picks or impact.

FIG. 17 illustrates a bifilament yarn in the transverse direction.Comparing FIG. 17 with FIG. 15, item be observed generally thereis a farlower increase in loading in the transverse direction for a given degreeof elongation than there is in the lengthwise direction. It is, however,an unexpected advantage of the bifilament yarn, that it has a definiteand significant loading capacity even at elongations as low as 3 percentwhich still remain adequate after six cycles of extension.

FIG. 18 shows exactly the same transverse stress-strain curve for afalse-twisted round cross section yarn. As can be noted at lowelongation, 3 to percent after six cycles, the false-twist yarn hasessentially no load-bearing capacity. Therefore, it would tend towrinkle. In a similar manner, a triangular cross section false-twistedyarn shows essentially the same initial transverse stress-strain curveas that for round cross section, and then very rapidly loads which is anindication of limited and narrow elastic characteristics.

FIG. 19 illustrates a bicomponent yarn in a transverse extension. Thisyarn also has very low load-bearing capacities throughout the rangetested up to 25 percent elongation. Again, if wrinkling should occur, itmore probably would occur with the bicomponent yarn of FIG. 19 than withyarn of FIG. 18, and especially with yarn of this invention illustratedin FIG. 17.

From the foregoing illustrations and comparisons made in connection withthe drawings, it can be seen that, in

general, the luster of bifilament yarns is a function of themodification ratio whether a glac look or a sparkle elfect is obtained.Other configurations show quite different luster effects and do notnormally demonstrate the silky high sheen characteristic of themodification ratios of between 1.65 and 2.0, and 2.05 to 3.0 which areillustrated in FIGS. 2 and 3. Many end-uses of knit apparel structuresrequire a low degree of transparency. To achieve this effect, anatasetitanium dioxide is dispersed in the monomer or at some point prior tocompletion of the polymerization cycle in the amount of 0.3 percent ofTiO by Weight of polymer for semidull articles and 2.0 percent by weightof TiO;; by weight of polymer for full-dull articles. This delusteringquality is desirable for its hiding power, but frequently it hasundesirable chalkiness or grayishness which decreases the aestheticproperties of the textile article containing said delustrant. Thus, whenthe bifilament yarn of this invention is made into knit textilearticles, an enhanced warmth of appearance and aesthetic propertiesisobtained. The delustered yarn has 10-20 percent greater cover on astandard hosiery form as compared with round cross sections ofequivalent denier. The high luster obtained for bright yarn has thefurther advantage in that the high degree of reflectivity which isobtained significantly reduces the apparent soiling as compared withround cross sections and triangular cross sections.

The following examples further illustrate the invention.

EXAMPLES l-14 The bifilamentary yarns of the present invention wereprepared from polycaproamide pellets of 50 to 65 relative formic acidviscosity which were spun-at a temperature of 255 to 270 C. from amelter through twin spinnerette orifices, 10 mils in diameter by 10 milsin length and separated from each other at a minimum distance of 2 mils.The metal web separating the two spinnerette orifices was counterdrilledfrom the spinnerette face for a distance of 3 mils. The spinneretteemployed had a counterbore angle of 60 as indicated by reference numeral5 in FIG. 1. The molten polymer entered the spinnerette counterbore atthe rate of 4.78 grams/minute/bifil filament. There were fourspinnerettes per stack, each spinnerette producing two strands ofbifilament yarn and each spinnerette was separately metered. Thus, eightstrands of hifilament yarn were produced per quench stack. The yarn wasquenched 3 inches below the spinnerette face with quench air entering atthe temperature of from 20 C. to 41 C. and traveled uniformly transverseto the filaments, at the rate of 10 lineal feet/min. for a distance ofinches from the point of initial gas contact with the filaments. Theyarn then entered a round quench stack of about 7 inches in diameter,thence over a lubrication roll where finish was applied at about 8 to 10percent by weight of yarn. The yarn was then taken up on a winder havingtwo cops per sleeve and using four sleeves per winder making a totalnumber of eight ends per winder having 4.7 pounds/ cop or 9.4pounds/sleeve. The speed of take-up was 1,950 feet/min. for the undrawnyarn. The bifilament yarn was then placed on drawtwisters passed 1.5wraps around an Armstrong Rubber Compound 732 cot roll having a 50-55Shore hardness, thence 4 wraps around a draw roll, thence to acylindrical core where a filling wind or pineapple wind was employed forhosiery. A wrap wind was employed for tricot and other sheer-typefabric. The rubber cot roll employed had a Shore hardness of 50. Ahigher value resulted in difliculty in maintaining the bifilament underthe cot roll.

The draw ratio between the cot roll and the draw roll was 3.98 and thedrawing speed was 3,050 feet/ min. The yarn contained about 0.2turn/inch twist and the drawn denier was 20. The weight of the yarn onthe pirns was approximately 2 pounds. The yarn was then placed on aLeesona 553 Superloft false-twisting machine and falsetwisted to a twistlevel of 31 turns/inch, at a heater temperature of 182 C. and a spindlespeed of 198,000 r.p.m. The yarn was fed into the twisting zone at aspeed 6 percent slower than it was discharged from the twisting zone.The final package weight 1 pound.

Round cross section polycaproamide yarn was prepared in a conventionalmanner, false-twisted with the same number of turns per inch as that forthe bifilament yarns for use as a control yarn. When delustered yarnswere desired, 03 percent TiO was added to the bifilament and round crosssection controi yarns. These yarns were knitted with a Textile MachineWorks Mark IV 400- needle 4 feed ladies circular knit hosiery machine,into hosiery 35 inches in length which contained 2,100 coursesthroughout the full length of the hosiery, for an average of 60 coursesper inch. The boarded hosiery contained at the ankle 74 wales per inchand 48 courses per inch. At the welt the hosiery contained 60 wales perinch and 66 courses per inch after boarding.

The polycaproamide yarns were boarded at a temperature of 118 C. forbifilament yarns and 108 C. for round cross section yarns, bothtemperatures being the maximum suitable for the particular cross sectiondescribed in order to obtain the best stretch properties.

The bifilament yarns of this invention were knitted utilizing a tuckstitch on a Fidelity 2-feed circular knit machine for production ofladies mesh knit hosiery for a comparison with hosiery of the sameconstruction utilizing filaments having a triangular cross section.

After preboarding, the luster properties of these hosiery weredetermined as well as some special bifilament yarns prepared underconditions to produce different cross-sectional modifications which aredescribed in Example 17. The method for obtaining luster values listedin Table 1 is given in the description herein. The interpretations as toquality of the appearance are based on the dyed hosiery placed over astandard leg form and the values are recorded as the average ofobservations (from a panel jury of 5 experienced colourists.Observations were made under fluorescent light and in bright daylight.Bright daylight assisted in showing the demarcation between sparkle andthe glace look of the hosiery. It was noticed by the panel jury ofjudges, that daylight emphasized sparkle, but subdued internal lightingemphasized the glac look. The ratings of the panel are listed in Table1.

The true visual rating for the increase in sheen for the false-twistbifilament yarns as compared with the nontextured bifilament yarns was200 to 300 percent greater at equal extension of a standard hosiery legform. The panel jury of experienced colourists rated the bifilamentyarns of this invention as having a sheer appearance value equal tobetween 10 to 12 denier rforthe 2O filament bi- The Instron was equippedwith G61-3C air-operated clamps gripping for a distance of 2 inches andthe two jaws were separated from each other by a distance orf 2 inchesin lengthwise tests and 1 inch in the transverse tests. The rate ofelongation was at 10 inches per minute on the loading part of the cycleand at the same rate on the unloading part of the cycle.

TABLE 1.OPTICAL OR LUSTER PROPERTIES AS MEASURED ON THE BOARDED HOSIERYAngle Percent 3 of bifilluster Modifiament K/S by cation intercept"color Type cross section ratio degrees eye Panel jury 4 Rating of thedegree of silky sheen glac look Bifilament 1. 4 62 6. No sheen, similarto round.

1. 65 55 10. 0 Good (A) subdues sheen. 1. 70 52. 5 -20% greater coverover Example 6A.

1. 8 49. 2 12.0 Excellent strong glac look high sheen. 1. 95 44 10-20%greater cover compared with Example 6A.

2. o 42. 5 14. 0 Good (B) glace look with slight Sparkle. 2.8 17 33.3Good (B) heavy point sparkles. 2. 5 27 24.0 No glac look, definitesparkle. 3.1 9 S lits and excessive sparkle higher. 1. 0 4. 5 o glaclook. 1. 0 Dull without warmth.

Heavy sparkle, too garish for most end-uses in hosiery. Heavy sparkle.

Good (A) subdued glae look.

Subdued sheen.

Excellent strong glac look.

Excellent strong iridescent point sparkle Scintilla look. Subdued warmsheen.

Good (B) heavy point sparkle.

No glace look".

No glac look, definite sparkle.

Glace look, too low a sparkle for sclntilla look.

1 Br=Bright hosiery. 2 (Dclustrant) SD=SemiduJl=0.3% by weight anataseT10 3 Luster is measured on the white boarded hosiery before dyeing.

4 The panel jury of 5 experienced colourists rating is based onobservation of the dyed hosiery, and is as follows:Excellent==Opalcseent smooth silky high sheen, the preferred glac look;Good (A)=Opalescent silky sheen glac look present but slightly subdued;Good (B): An opalesecent high sheen with the preferred "glac look" butsome sparkle present.

5 Too non-uniform to read.

No'rn. E-T==False twist.

TABLE 2.*FORCE IN GRAMS FOR HOISERY EXTENDED LENGTHWISE AT THE INDICATEDELONGATIONS 1 Percent Ankle elongation, percent Percent Knee elongation,percent Number work of ork of Example No. of cyles recovery 3 5 10recovery 8 6 10 16 20 25 9. Bifil false-twist standard knit 1 69 3 18 2748 78 113 145 58.3 18 22 32 45 58 75 stretch hosiery 6 64. 2 10 16 34 63100 136 63. 2 8 12 23 36 52 70 11. Round filament false-twist 1 43.7 1420 40 63 87 113 54.0 12 17 30 47 65 78 standard knit stretch hosieryL... 6 50. 5 2 5 22 43 72 103 56 4 3 7 19 36 55 73 13. Bicomponentstandard knit 1 44.6 18 25 50 6 137 200 53 2 18 25 72 105 [42 stretchhosiery 2 6 48. 2 4 12 32 67 121 195 58 1 7 12 30 66 95 135 7A.Triangular cross section falsetwist 2 6 52.0 1 25 80 105 47.1 3 12 22 403. Bifilament cross section standard 1 4.4 300 400 800 1,200 1,700 2,30045.0 300 500 850 1, 320 2 000 knit hosiery, Nylon 6 2 6 9. 0 50 60 3001, 300 2, 100 60 4 50 350 800 l, 500 6. Round cross section standard 139. 0 400 650 1,300 2, 000 2, 800 3 600 41 0 300 500 950 1,350 1,800knit hosiery, Nylon 6 6 56.0 50 400 2,100 3, 300 52 2 50 450 80 1.40014. Bifilament cross section mesh- 1 40.6 450 800 2,000 3 400 5,0006,500 45 7 200 350 650 1,100 1,700

knit, Nylon 6 4 6 7- 5 500 1,800 3, 700 6 200 61 2 300 600 1, 300 7.Triangular cross section mesh- 1 38.7 500 1,000 2,200 3,520 4,900 6,25041 1 200 320 700 1,200 1,800

knit, Nylon 6,6 6 58.5 400 1,700 3,600 5, 800 58 8 200 600 1,350

1 The values in the table are all expressd in rams with the exception ofwork of recovery.

2 Standard knit, plain or jersey stitch.

3 Load too small to show on chart.

4 Mesh knit =tuck stitch.

5 Too small to read on Instron on 10,000 gram load scale. filament. Thisproperty is of significant value since it means that the bifilamentyarns have an improvement in sheerness values of 165 percent Without aloss in wearing properties as would normally be expected with acorresponding reduction in the denier typically required in round crosssection hosiery to achieve the present sheerness values.

The improvement in Sheerness is due to alignment of the concave surfacesfacing each other at stitch crossing points so as to present the narrowedge to view.

All luster values listed in Table 1 were ascertained using a color eyefabric sample holder with a black background and employing a Model D-lColor-Eye.

The boarded stockings were dyed in a conventional manner, dried by thetray method and placed in an Instron tester to evaluate the stretchproperties of the hosiery. The hosiery were pretensioned at 1 percent ofthe total Instron loading which was 100' to 500 grams minimum and 2,000grams maximum. Thus, the pretensioning was between 1 to 5 and 20 grams,depending upon the degree of stretch in the hosiery being tested and theloads required to elongate the hosiery to 25 percent.

Work of recovery is the ratio of recoverable work to the total workrequired to strain a fiber or fabric a specified amount under a givenprogram of strain rate. In this case, it was determined at 25 percentelongation 15 seconds forward cycle, 15 seconds return and wascalculated according to ASTM D-1774-64, ASTM Standards (1964) part 25,pp. 428-432.

All values for Tables 2, 3, 4 and 5 were measured using Instron G61-3C2-inch rubber faced air operated jaws clamped with 60 pound pressure.The cross head and gage length were the same and a 25 percent elongationwas achieved in 15 seconds. There were 2 inches of hosiery between theclamped jaws and lengthwise tests and 1 inch of hosiery between clampedjaws in the transverse or width tests.

The bicornponent and triangular yarns evaluated herein are soldcommercially.

The elastic properties of the hosiery on lengthwise extension are givenin Table 2. As can be seen the ankle and the knee areas were selectedsince these are the areas of greatest wrinkle problems in ladieshosiery.

Referring to the results shown in Table 2, it can be noted that thebifilament false-twist yarns have the highest work of recovery of allyarns tested and the improvement in terms of work of recovery is thegreatest after 6 cycles when compared to other types of yarns tested asindicated by Example 9. Most significant in the stress-strain curve wasthe stress force at an elongation of 3 percent. It can be noted that thehosiery of Example 9 had a stress force of 16 grams which was 250 to 500percent higher loading in the ankle area at 3 percent elongation thanthe round cross-section false-twisted yarn (Example 11) or bicomponentstretch hosiery (Example 13). Without false twist, the bifilament crosssection, plain knit or jersey knit hosiery (Example 3) may be comparedwith the round cross section yarn (Example 6). The work of recovery onthe first cycle is 44.4 percent or percent higher for the bifilamentcross section than the round which would indicate definitely improvedwrinkle resistance. In Table 2, it can be observed further that thebifilament cross section yarn (Example 3) has a greater elasticity after'6 cycles of extension than the round cross section of plain knit andless force is required to extend it to 25 percent. Indeed, the stressforces are about /2 that required to extend round cross section yarn ofan equal denier. After six cycles of extension the bifilament crosssection plain knit hosiery has a stress force of 50 grams whichindicates excellent capacity to retain its shape, whereas the roundcross section has an immeasurably small value.

Bifilament yarns containing 0.3 percent TiC); and 2 percent TiO wereconverted to false-twist yarns similar to that described for Example 9and exhibited similar elastic properties in test hosiery as thatillustrated in Table 2 for Example 9. Likewise, bifilament cross sectionyarns containing 0.3 and 2.0 percent of TiO were converted to standardjersey knit hosiery. The bifilament yarns containing TiO exhibitedsimilar elastic properties as that of Example 3. The bifilamentfalse-twist yarn of Example 9 might be additionally compared with thetriangular cross section false-twist yarn of Example 7A in the form ofsimilar hosiery. As can be observed, the work of recovery for thetriangular cross section falsetwist yarn is significantly less thanbifil false-twist yarns and the elongation after six cycles at 3 percentelongation was 1 gram compared with 10 grams, or about 10 percent ofthat obtained for the bifilament yarns at the ankle section of thehosiery.

Likewise, the triangular cross section yarn h'osier/ in the knee sectionhad significantly less work of recovery and very low load to O loads at3 percent elongation-than did the biflament cross section of Example 9which had a stress force of 9 grams when tested in the knee section.Thus, it should be expected that the triangular cross section yarnsgenerally would have greater problems with sagging and wrinkling thanwould the bilfilament yarns of this invention.

Examples 14 and 7, respectively, show a comparison of bilfilament crosssection with triangular cross section in a mesh knit stocking.Generally, the elastic properties are approximately equivalent to thetriangular cross section in the mesh knit hosiery. It is believed thatfailure to show equivalent advantages here may be due to tuck knitstitch on long courses having reduced twist and,

14 consequently, this type stitch interferes with the ability of thisyarn to twist at stitch doubling areas.

The data for Examples 9, 11 and 13 are shown graphically in FIGS. l5, l6and 14, respectively, and the picture of the knit hose of Example 9 isshown in FIG. 8, Example ll in FIG. 10, and Example 13 in FIG. 12.

The bilfil cross section mesh knit hosiery has 5 to 10 percent greaterwork of recovery in the knee section than does triangular cross sectionmesh knit yarn, both being made employing a tuck knit stitch. After sixcycles, the bilfil cross section appears to retain 50 percent more forcein the knee section at 10 percent elongations. However, in Table 3, itcan be observed that in the transverse direction, the bilfilament meshknit hosiery after six cycles, has a stress force of 10 grams at 3percent elongation and at the knee seciton and at the welt section.Additionally, after 6 cycles, the power of recovery (see Table 4) of thebilfil mesh knit in the lengthwise knee area was 150 grams or 150percent greater than that for the triangular cross section.

In Table 3, bilfilament false-twist yarns (Example 9) are superior toround false-twist yarns (Example 11) and bicomponent round cross section(Example 13) in plain knit in a transverse direction over the entirerange of elongation and at 25 percent elongation, especially after 6cycles of extension. The values vary between 200 percent and 100 percenthigher for Example 9 than for Examples 11 and 13 in the transversedirection. For bilfilament plain knit hosiery (Example 3) as comparedwith round plain knit standard hosiery (Example 6) it can be observedthat the transverse force elongation values are much higher and wouldrepresent a more comfortable extension force than that obtained forround cross section. After 6 cycles, the values for the bifilament wereadequate to avoid wrinkling and obtained a smooth fit in the ankleregion and in the knee region.

Example 7A, triangular cross section false-twist yarns had similarproperties in transverse direction to that of the bicomponent yarns upto a 10 percent elongation; however, at 10 percent elongation and above,very rapid loading ensued which indicated a lower degree of elasticityfor the triangular cross sections of this yarn. Table 4 illustrates amore significant part of the elastic properties. In this case the yarnwas extended to 25 percent elongation and allowed to return to 12 /2percent elongation and the force in grams ascertained at this point byreading from the chart. This value is designated as the power ofrecovery, and is frequently referred to as the muscle power of thefabric and is probably a more significant value than is the forwardextension part of the cycle. As can be observed in Table 4, bifilamentfalse-twist stretch hosiery (Example 9) after six cycles of lengthwisestrength has a power of recovery of 25 grams or 300 percent greaterforce at the ankle as compared with the bicomponent round cross sectionfalsetwist stretch yarn. Additionally, the bilfilament yarn hassignificantly higher values in the knee section.

In Example 9, bifilament false-twist stretch hosiery after six cycles oflengthwise stretch has at least 200 percent greater force at the ankleas compared with a triangular cross section (Example 7A) false-twiststretch hosiery of identical construction.

TABLE 3.HOSIERY PHYSICAL PROPERTIESTRANSVERSE Below-welt-thigh areaelonga- Ankle elongation, percent tion, percent Number Example No. ofcycles 3 5 10 25 3 5 10 25 9. Bifil F.T. 6 5 7 12 50 5 7 15 11. RoundF.T. 6 1 3 6 26 2 7 50 13. Bicomponent 1 U 6 3 6 15 3 5 10 26 7A.Triangular cross section F31) 6 2 5 125 3 3. Bifil plain 1 6 5 10 50 5550 6. Round cross section 1 6 4 10 5 80 460 14. Bifil mesh knit 6 5 1040 380 10 10 30 570 7. Triangular mesh knit. 6 5 10 35 5 8 270 1 Plainor jersey knit. 1 Mesh knit or tuck stitch hosiery.

Norm-F31. False twist.

A similar improvement for Example 9 over Example 11 and Example 13 canbe observed for the power of recovery in the transverse direction. Thepower of recovery for bifilament yarn (Example 3) in the knee section is125 grams or approximately twice that of the round cross section(Example 6) in the lengthwise direction. The power of the recovery of175 grams for bifilament cross section mesh knit yarn (Example 14) isapproximately twice that for the triangular cross section mesh knithosiery (Example 7) after 6 cycles of extension.

It is observed that the bifilament yarns (Examples 2, 3, 8, 9 and 10) ina ZO-denier exhibited approximately the same sheerness of that observedfor a 10-denier monofilament. This is because bifilament yarns wherethey cross at the stitch point present the narrow edge of the bifilamentto view. Thus, at the point of maximum abrasion or compression onepresents the best geometric area for breaking resistance whiletheminimum geometric area is presented to the eye, thereby achievingsheerness and simultaneously good wearing qualities of the hosiery.

Panel jury tests of women in wear tests of a single TABLE 4.POWER OFRECOVERYEXTENSION TO ELONGATION WITH MEASUREMENT OF LOAD ON RETURN TO12%% ELONGATION Transverse or width direc- Number Lengthwise of hosiery1 tion of hosiery 1 Example N0. cycles Ankle Knee Thigh Ankle Knee Thigh9. Bifil false-twist 2 Q 11. Round cross section false-twist 2 g g 5 513. Bicomponent round cross section 2 "5:5 "5 "5 7A. Triangular crossSection false-twist 2 6 12 7 1 250 150 l 0 Blfil hmery 2 6 13% 125 12020 40 50 1 2 100 0 Round Slew 2 "1 6 50 so 50 20 1o 1 50 200 50 it.Bifil mesh knit 6 250 175 250 26 7. Triangular mesh knit sparkle yarn288 $8 1 Force in grams after extension to 25% elongation and return to12 elongation is designated the power of recovery. 3 glaiai or jerseyknit.

0 ate.

TABLE 5.MAXIMUM ELONGATION OF HOSIERY, STRETCH AT ANKLE Percentelongation, after one cycle Where 500 1, 000 yield 2, 000

gram gram point gram Example No. load load occurs 5 load 9. Bifilfalse-twist stretch hosiery. a. 85 101 84 120 11. Round false-twiststretch hosiery." 84 98 80 118 13. Bicomponent round stretch hosiery 3656 36 80 This value was obtained in the test procedure similar to thatfor the yield point in yarns where a straight line is taken alonginitial load line, then a similar straight line is drawn at maximumloading or stress to bisect the first line drawn and then a straightline from this intercept with the stress-strain line drawn by theInstron. This intercept point is called the Yield Point.

From Tables 2 through 5 the following general conclusions may be drawn:

(1) Bifilament false-twist yarns (Example 9) on repetitive cycling havesubstantially improved elastic properties as compared with Examples 11,7A and 13 over the entire range of tests evaluated.

(2) Bifilament cross section yarn in standard knit hosiery (Example3)--, as compared with round cross section in standard knit hosiery, hassome slightly improved properties after 1 cycle and significantlyimproved properties after 6 cycles over the entire range evaluated.

1 (3) Bifilament cross section mesh knit hosiery (Example 14) has equalproperties over most tests employed and slightly" to' significantlyimproved properties after 6 cycles of testing as compared with atriangular cross section mesh knit hosiery.

size hosiery made of false-twist bifilament yarns (Example 9) rated themas sag-free having excellent wearing qualities and having exceptionalaesthetic qualities in appearance. They rated the comfort fit over anentire range of leg sizes of 8% to 10 /2 as excellent. The wearingqualities were quite superior to other hosiery such as Example 11,false-twist round cross section hosiery, Example 7A triangular crosssection false-twist hosiery, and Example 13 bicomponent standard knitstretch hosiery. The bicomponent hosiery in all examples were composedof nylon 6,6 as the sheath portion which is about 35 percent by weightand nylon 6,106,6 copolymer in the core portion generally in the kidneyshape as 65 percent of the total.

The above hosiery fashioned from bicomponent and triangularcross-section yarns were purchased for comparative evaluations.

EXAMPLE '15 Bicomponent yarn was prepared by the procedures described inExamples 1-14 except nylon 6,6 was employed. The bifilament yarn wasfalse-twisted and compared with similar hosiery made from false-twistround cross section yarn. These were tested for work of recovery, andstressstrain curves similar to those indicated in Tables 2, 3, 4 and 5.The bifilament hosiery made from polyhexamethylene adipamide showedapproximately equivalent improvement in all physical properties and inluster effects as that already described for polycaproamide whencompared with the round cross section made under identical conditionsexcept with respect to the spinnerettes employed.

The spinning temperature was maintained at about 280 C. to produce agalc look from the polyhexamethylene adipamide (nylon 6,6)

EXAMPLE 16 Poly [bis (para-aminocyclohexyl methane dodecamicles] wasspun at a temperature of 290 C. through bifilament spinnerettes of thetype illustrated in FIG. 1 and was drawn at a draw ratio of 3. The drawnyarn had a density of 1.001; a moisture absorption of 3 percent at 65percent relative humidity and a glass transition temperature of greaterthan C. This yarn was also prepared in round cross section. The sameimprovement in elastic properties for bifilament cross section inhosiery after twisting over the control in round cross sectionwas-noted; however, the elastic properties as compared withpolycaproamide and polyhexamethylene adipamide was approximately twiceas great in the force in grams at low elongations of 3 and percent. Thework of recovery was between and percent higher than that indicated forpolycaproamide. The muscle value or power of recovery was approximately100 percent greater than the polycapoamide listed as Example 9, Table 4,for the ankle, knee and thigh dimensions.

These values are desirable for support hosiery but too high forconventional stretch hosiery, for a comfortable fit.

EXAMPLE 17 A series of runs was made employing polyamides of relativeformic acid viscosity of to 90 using a spinnerette of the typeillustrated in FIG. 1. A range of temperatures from 250 to 290 C. wereevaluated. The distance between the spinnerette orifices tested was from0.9 to 4.0 mils. Heated quench air immediately below the spinnerette wasevaluated in the range of 260 to 350 C. and the velocity of the quenchair in the vicinity of A to /2 inch from the spinnerette face wasevaluated in the range of 0 to 8 standard cubic feet/minute/ZS poundsper hour throughput. Polymer throughput was evaluated at a high rate, 8grams/minute/bifilament and at a low rate of 2 grams/minute/bifilament.The spinnerette orifice length of 20 to 150 mils was evaluated.

In Table 6 are the results of these evaluations in order to optimize theglac look.

The web separating the twin capillaries was counterbored from thespinnerette face for a distance of 5 mils to' provide initial moltenstream contact and avoid bifilament splits at high modification ratios.The spinnerettes employed have straight-sided counterbore. Normallyfnoheat is required in the vicinity of spinnerettes, but in this case, itis desirable to have a high melt viscosity polymer and small spinneretteorifices. Thus, the role of the heated ring is for good spinnability andto avoid splitsdue to irregular movement of the yarn at the capillaryexit.

The yarn was contacted approximately 9 inches below the spinnerette by200 cubic feet/mimof gas which was difiused into the quench stack for adistance of 2 feet along the outer peripheral of the 48 inch quenchstack so that the maximum lineal velocity of the quench gas is 8'feet/min. Thirty cubic feet/min. of gas is exhausted up: wardscountercurrent to the flow of the filaments and out through monomerexhaust ports, located approximately even with the spinnerette. Adistance of A to /2 inch separated the spinnerette face from theresistance heating ring. The velocity of the exhaust gas was less than 2lineal feet/min. The quench gas then travels cocurrentwith the filamentand was exahusted at a point approximately 17 feet below the spinneretteface. The 168 ends of yarn were passed over a single finish roll groovedto act as a guide for the 168 ends. To each filament was applied 8 to 10percent by weight of finish emulsion equal to about 1 percent of finishoils. The yarn then contacted a take-up roll having a peripheral speedequal to 1000 ft./ min. and thence passed over draw rolls traveling at alineal speed of 4,000 feet/min. Three wraps were taken on the draw rolland three wraps were taken on the take- TABLE 6.-PROCESS FOR CONTROL OFMODIFICATION RATIO Approx- Signiflimate Glace-look" "Scintilla look"eance relative Assuming I level etiect value Range Preferred RangePreferred Polyamide relative formic acid viscosity 1 100 Increases 25-65-60 40-90 58-75 Mils between spinnerette orifices 2 90 do 0. 9-3. 0.. 1.5-2. 5 2. 5-4. '2. 5-3. 5 Temperature, C 3 6O Decreases. 270-280 260-280Heated quench, 0 medium immediately below spinnerette- 4 30-40 o Quenchair rates in the vicinity of the spinnerette 5 25 Increases. 0.1-1.0..6-8

s.c.t.rn s.c.f.m. Polymer throughput 6 20 Decreases. High Low.

spinnerette orifice capillary:

Length effects 7 10-15 Inereases Short Short Long Long. Length in mils8- 0 8-150 8-150 20-150 Length/diameter 0.8-3. 0.-.. 0. 8-2. 0.... 2-202-10 1 On mod.- ratio, percent as compared with 1. 2 On left increaseseffect on modratio.

3 4-8 grams per minute per bilfil filament.

4 2-6 grams per minute per bilfil filament orifice.

EXAMPLE 18 Polycaproamide pellets containing 1.5 percent extractables of0.1 inch in diameter by 0.1 inch in length were melt spun through abifilament spinnerette orifice as a type indicated in FIG. 1. Thepolymer was melted in a 4 /2 inch extruder at a temperature of 255 to265 C. and extruded at the rate of 456 pounds/hour and fed to 8 quenchstacks. Each quench stack contained 42 spinnerettes, each spinnerettewas subdivided and contained openings for production of 2 bifilamentyarn ends on each side of the partition wall. The quench stack contained168 ends of bifilament yarn and each yarn end was spun at the rate of0.3 pound/hour/end. Thus, each quench stack produced 57 pounds/hour of20-denier drawn monofilament yarn.

A peripheral ring of 42 spinnerettes was surrounded with gas maintainedat a temperature of 260 C. by two resistance heaters forming a ring oneither side of the spinnerette. Each twin orifice had a capillary 10mils in diameter x 30 mils in length and these twin capillaries wereseparated from each other'by a distance of 2.6 mils.

5 Capillary length is proportional to diameter, thus a larger diameterrequires a longer length. A better characterization of this is thespinnerette capillary length divided by the spinnerette capillarydiameter. 7 v

up roll. Take-up rolls and draw rolls were dual rolls and were cantedtoward each other 3 to facilitate separation of the wraps. Quartering ofthe quench stack provided for approximately 10 spinnerettes per quarter.The varn then passed from the draw roll over a heater 98 inches long ata speed of 4,000 feet/min, thence to false-twist spindles of the typedescribed in UK. Pat 931,837 dated July 7, 1963 which combines frictiontwisting superimposed upon top of the normal rotational speed of 350,-000 rpm. Two ends were passed through in opposite directions on eachtwister spindle and threaded up as indicated in the aforesaid patent.The residence time on the 98 inch heater was 0.12 second. The yarn thenpassed through discharge rolls were the twist was released, saiddischarge rolls having a peripheral speed of 4,250 feet/ min. The yarnwas then taken up on a special surface driven winder, which drove 4sleeves on each of its 4 quarters, each sleeve contained 3 cops and eachcop contained 2 ends. Thus, 24 ends were takenup oneach of the 4quarters of the winder. Each sleeve was separately d0f' fable from thewinder and each winder-took up 96 ends;

The area occupied by the winder was 24 inches on center. Thus, 2 windersaccommodated the output of the quench stack.

The r.p.m. of the spindles plus the fractional twist was equivalent to1.5 million rpm. to apply 31 turns/inch at the 4,000 feet/min.

The quality of this false-twisted yarn was somewhat superior to thatdescribed in Examples 1 through 14, because of greater uniformity oftwist and general freedom from defects which are characteristic of acontinuous operation as opposed to a multiple-step operation asdescribed in Examples 1 through 14.

This yarn when knitted into hosiery had essentially the same elasticproperties of that described for Example 9, since the elastic propertiesare the result of the novel filament cross section and the twist turnsemployed rather than the precise process employed in its manufacture.

Alternately, in place of the false-twist spindles as described in UK.Pat. 931,837, is the false-twist friction device built by Zimmer TextileMachine Works, Gmbh West Germany and described by Man-Made Textiles andSkinners Record, September 1967, pp. 110-112. When this this unit isoperated at a spindle speed of 20,000 r.p.m., and the friction device isoperated at maximum speeds, up to 3,000,000 turns/minute can be impartedto filaments. It is preferred, however, to run the spindles at higherspeeds and the friction twist device at lower speeds 11 order to obtaina more uniform twist.

. Since tricot knits have a stitch very similar to the plain knit, e.g.,jersey knit stitch, fabric made by tricot knitting exhibits similarelasticity utilizing the bifilament yarns of this invention. Generally,it can be said that tricot fabrics have about 50 to 60 percent lesselasticity than jersey knit products. By using bifilament yarns, one canachieve approximately equivalent elasticity in the tricot knit wear asthat obtained for jersey knitted round cross section yarns. Thisrepresents a substantial improvement in the elasticity for tricot knitwear. These bifilament yarns find utility in womens slacks, swim wear,in leotards and the like, where the characteristics of subtle iridescentsparkle combined with the elastic properties considerably enhance theutility of the textile article made from bifilament yarns. Particularlywhere sheer fabrics and styling are desirable such as in intimate wear,e.g., nightgowns, housecoats, lounge suits, negligees, peignoirs, andthe like, these bifilament yarns have high utility. Tricot knit fabricsand other flat fabrics maybe further modified in appearance by employingthe processes known as schreiner calendering where the angle and size ofthe grooving employed tends to increase the contrast thereby resultingin an increase in sparkle. Generally, bright and pastel colors favor thescintilla look. The acid dyes and fluorescent dyes insure that thesparkle look is emphasized in the finished articles. In mixed fabrics,dark areas decrease the scintilla look and bright dyes increase thescintilla look. Polyamides having amine end groups of 2030 may be dyedwith basic dyes using a pH of 7. Polyamides having amine end groups of40-50 may be dyed with basic dyes using a pH of 8.

The effect of dyestuff on bifilament textiles in order of decreasingsparkle emphasis is as follows: fluorescent dyes, basic dyes, acid dyes,premetallized dyes and disperse dyes. Other means of increasing thescintilla look are plaiting of the bifilament yarn on the front ofdarkcolored backing yarn. Also, a considerable increase in the scintillalook can be obtained by doubling the number of bifilament yarns n theface of courses. An opposite effect is obtained if one doubles thenumber of yarn ends creases the point sparkle. A patterned designgenerally increases the sparkle.

EXAMPLE 19 Bifilament yarns produced in accordance with Example 3 except40 denier monofilament was produced instead of 20 denier monofilament.The 40 denier monofilament had a modification ratio of 2.4. This wasplaced in tricot knit automotive upholstery having the following yarns:first bar, round cross section nylon, 140 denier/24-fila-. ments bright;second bar, round cross section nylon, 70 denier/ 12 filaments semidull;third bar, bright filament cross section nylon 40 denier/1 filament.This tricot fabric when bent in daylight, showed a sparkling shim-meringsheen where each individual bend of the bifilament yarn appeared asminute point sparkles or scintillas. The alignment and order of thelight reflectance was similar to that shown in hosiery and it is thisalignment of the point sparkle which produced a subtle and pleasingshimmer. The sparkle resulted in warmness of fabric appearance withoutgarishness which distinguishes it from prior art novelty sparkle yarns.The tricot fabric had a 5 percent increase in elastic stretch propertiescompared to a fabric of like construction utilizing a round crosssection yarn.

It has been found that the high luster and high sheen characteristics ofthe bifilament yarns of this invention, whether false-twisted or othertexturing systems are employed, the reflectivity is relatively unchangedafter washing from the original textile article prior to soiling.Therefore, the apparent soiling of such fabrics is largely overcome by aminor reduction in the sheen and the general appearance with respect tosoiling is considerably superior to other cross sections such as found,triangular and the like although treated in the similar manner. Thisproperty is of particular value in White intimate wear and in pastelcolors which would otherwise show considerable soiling in cross sectionsemployed heretofore in the prior art.

While the production of the bifilament yarn product of the presentinvention has been illustrated utilizing separate orifices, thoseskilled in the art will recognize that other types of orifices may beemployed. For example, two holes connected by a thin slot may be usedthrough proper control of spinning conditions which achieve a bifilamentas described herein.

We claim:

1. A method of producing polycaproamide bifilament yarn having improvedphysical and optical properties for use in ladies hosiery consisting ofextruding molten polycaproamide having a relative formic acid viscosityof about 50 to 65 units at a temperature of from about 255 C. to 270 C.through twin spinnerette orifices, said orifices having a diameter ofabout 10 mils and a length of about 10 mils and being separated fromeach other by a distance of about 2 mils and interconnected at the polymer exit surface by a width of not greater than 40 percent of theorifice diameters, the molten polymer entering the spinnerettecounterbore at the rate of about 4.78 grams/minute/bifil filament,quenching the polycaproamide yarn at an entering air temperature rangingfrom about 20 C. to about 41 C. starting at a distance 3 inches belowsaid orifices to a distance of inches below said starting distance at agas lineal velocity of about 10 lineal feet/minute, fusing thepolycaproamide bifilament yarn wherein symmetrically opposed concavesides are formed that intercept at an angle of from 38 to 54 degrees andhave a modification ratio between about 1.75 and about 195, said methodbeing further characterized in that the polycaproamide bifilament yarnis extruded at a lineal speed of about 1,950 feet per minute, drawn atabout 3.98 and subjected to false twisting to a twist level of about 31turns/inch.

2. The method of claim 1 wherein the concave sides of the bifilamentyarn intercept at an angle of 46 gr es.

of the bifilament yarn intercept at an angle of 49.2 degrees.

21 22 3. The method of claim 1 wherein the concave sides 3,470,68610/1969 Fleming et a1 57140 3,528,128 9/1970 Murakami et a1 18-855References Cited FOREIGN PATENTS UNITED STATES PATENTS 5 791,468 3/1958Great Britain 264-177 F g F 816,877 7/1959 Great Brltaln 264-177 F al gF 1,112,938 5/1968 Great Britain 264-177 F i gfl 264M177 F 1,023 2/1963Japan 264177 F Jamiesoniiiii 264-177 F 9,535 5/ Japan F Opfell 264 177 F10 Luzzatto 264,477 F JAY H. WOO, Primary Examiner 'Privott et a1.264177 F McIntosh et a1. 264177 F o f ll 2 4 177 F 161-177; '264-21O F;425-464 2 23 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 317371505 Dated une 5, 1973 I o Garland L. Turner et al.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 1, line 20, "preefrab'ly" should be -preferably-'.

Column 3, line 28, "warps" should be wraps. Column 4, line 36,"elastically" should be -elasticity.

Column 4, line 53, "yarns" should be yarn-Q Column 5, line 48, "lost"should be --lose Column 6,- line 1, "filament" should be -bifilament-iColumn 6, line 2, "significant" should be ----significantly-. 1

Column 8, line 2, "trifiament" should be trifi lament'.

Column 10, line 19, "wrap" should be warp.

Table 2, under "Percent Work of Recovery", Example No. 3, "4.4" shouldbe 44.4.

Table 2, under "Ankle Elongation, 1 Example l3, "6" should be -86--.

Signed and sealed this 8th day of January 197R.

SEAL) Attest:

EDWARD M.ELET0EEE,JE. RENE D. TEGTMEYER Attesting Officer ActingCommissionerof Patents

